This.
Also there are anomalies. The bottom girls in this list all have 117.05M base, but to level them, the cheapest is Judy and the increase in cost is bigger for all the others. So big, that currently it does not seem to be beneficial. "currently" is below 6000 total level of all 11 girls. If someone has any insights, that would be apreciated.
The other is Amanda and Zoe. They have the same base too. And here the cheaper girl stays cheaper to level.